This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to understand how ordinary doses of aspirin affect platelets. Platelets are blood cells that control blood clotting. Aspirin can be helpful in prevention of heart attacks and stroke, largely because of its effects on platelets. Your blood may be tested for blood proteins, blood cells, and a variety of genes.